1. Field of the Invention
The present invention relates to a thin-film magnetic head that comprises a closure and makes contact with a magnetic recording medium during read and write operations, a head gimbal assembly (HGA) with the thin-film magnetic head and a magnetic recording apparatus with the HGA and the medium. Further, the present invention relates a manufacturing method of the thin-film magnetic head.
2. Description of the Related Art
A magnetic disk drive apparatus such as a hard disk drive (HDD) or a flexible disk drive (FDD) is a representative example of the magnetic recording apparatuses, which is portable and lower in price per byte than semiconductor memory. Recently, because the volume of various data becomes larger due to the spread use of the multimedia and the Internet, the magnetic disk drive apparatus is strongly required to have much larger capacity and to be further miniaturized.
In the situation, a contact-type apparatus is worth noting because of its possibility of higher recording density. The contact-type apparatus has, for example, a loading mechanism for transferring an inserted cartridge including a disk to the predetermined position, a rotary drive mechanism for holding and rotating the disk in the transferred cartridge, a magnetic head device for writing data signals to the rotated disk and reading data signals from it, and a moving mechanism for moving the magnetic head device in the radial direction on the disk.
The magnetic head in the magnetic head device writes and reads data signals in contact with the magnetic disk. A Metal-In-Gap (MIG) head has conventionally used as the contact-type head. However, in order to respond the increasing data storage capacity and the further miniaturization of the magnetic disk drive apparatus, a thin-film magnetic head for an HDD, which inherently meets higher recording density, is being applied to the contact-type apparatus. The thin-film magnetic head for the HDD has a structure suitable for flying on the magnetic disk without contact during read and write operations. Therefore, the simple use of the thin-film magnetic head under the contact condition may cause a significant wear or crash of the head. To avoid the problem, U.S. Pat. No. 6,947,259 proposes the limitation to a predetermined range of the distance between an electromagnetic transducer (magnetic head element) and the contact edge of an overcoat layer. Further, Japanese Patent Publication No. 06-309625A describes a contact-type head for perpendicular magnetic recording with the sliding surface of an antiwear layer.
Furthermore, U.S. Pat. No. 5,142,768 and Japanese Patent Publications Nos. 08-321012A and 06-012622A describe a magnetic head used for a magnetic tape drive etc., which has a bonded protection plate such as a closure block.
However, when the “closure-type” miniaturized magnetic head is used for a magnetic disk drive apparatus such as a FDD, a recess is likely to be generated in the end portion on the opposed-to-medium surface side of an adhesive layer that bonds the closure, which may cause a negative effect about sliding operation.
In the use of the “closure-type” magnetic head, the closure makes repeated contact with the magnetic disk rotating at high speed. In addition, the adhesive area cannot be avoided to become small due to the miniaturization of the head for higher recording density. For these reasons, the adhesive strength of the closure is required to be sufficiently high. As a method for enhancing the adhesive strength, Japanese Patent Publication No. 08-321012A describes a technique in which fine grooves are formed on the adhesive surface of the closure or the protective layer of the head elements to improve the adhesive strength.
When this technique is used, the thickness of the adhesive layer is usually required to be at least 0.4-0.5 micrometer (μm) to obtain the sufficiently high adhesive strength. However, the adhesive layer with such a large thickness is likely to cause a recess to be generated in the end portion on the opposed-to-medium surface side of the adhesive layer by the action of abrasives during finish polishing of the opposed-to-medium surface. As a result, the recess portion has some possibility to catch and hold fine dusts, which may cause a negative effect about sliding operation between the head and the medium.
Meanwhile, in the case that the adhesive layer has less thickness, it becomes difficult to obtain the sufficiently high adhesive strength, and further, variations in the thickness of the adhesive layer among manufactured heads, that is to say, variations in the adhesive strength become larger. As a result, the reliability of strength in the thin-film magnetic head is likely to deteriorate and the manufacturing yields may be reduced. Furthermore, when a large pressure is applied to the closure during adhesive process to make the adhesive layer thinner, some disadvantage, such as a contamination of electrode pads, is likely to occur due to the protrusion or running off of the adhesive.